I want to make an animated movie

[Neyski]

I remember using Moviesetter back in the day...Good luck man!

Speaking as an animator, 20mins is a TON of animation to do, a drawing tablet will be a good investment.

[Neyski]

DPS PAR is for outputting to video tape isn't it? (Speaking out of ignorance here, I've never owned one myself)

I've been using deluxe Video to stitch together DPaint anims with sound, don't know if it will help with your memory limitation issues though...